River Skaters Aquarius najas along the River Teme
Skating on the Teme; the age of Aquarius?
On June 8 2013, I joined a group of naturalists including Rosemary Winnall, Mike Averill, John and Denise Bingham, Jane and Dave Scott and Will Watson on a visit to Burford House near Tenbury Wells on the river Teme. Our objective was to look for sea lamprey which have been reported spawning in the river gravels nearby. As we scanned the Ledwyche Brook which flows into the Teme at Burford House grid reference SO582679, I noticed a couple of large skaters on flowing water around a mass of twigs. They were clearly larger than pond skaters, Gerris and appeared very much at home on the flowing water. We tentatively identified them as River Skaters Aquarius najas, a species I had not seen in Worcestershire before. I still haven’t because frustratingly they were just inside Shropshire, about 50m from the county boundary. Had they been a few metres downstream on the main River Teme, we could have claimed them for Worcestershire, but although we searched there we didn’t find any.
Further west near Little Hereford church, we struck lucky and Rosemary Winnall and I were able to photograph and identify River Skaters on the main Teme where a few were in backwaters below the footbridge behind the church at grid reference SO554678. But here we were much farther from the Worcestershire boundary, though they must surely frequent parts of the Teme in that county. The species has an odd distribution in the UK, where it is often common on Welsh streams and rivers and also occurs in the New Forest, but is scattered and very local over most of midland and eastern England. It is rare in Shropshire with a few recent records from the north of the county and in Worcestershire: the only record I can find on NBN Gateway is a lonely red dot on the Drayton Brook near Belbroughton. Have we overlooked them elsewhere?
With a good view river skaters are easy to identify from their habitat, nearly always occurring on flowing water though they will frequent canals. Their size is usually obvious: body length is 13-17 mm compared with 8-10mm for common pond-skaters Gerris lacustris. River Skaters usually have no wings even when mature in the UK and so have limited powers of dispersal. They seem to prefer stony banks and streambeds and hibernate as adults among waterside stones. Overwintered adults pair in late spring and according to Southwood and Leston (1959), males will ride piggy-back fashion on their mates for several weeks throughout summer, sometimes sharing food with their partners.
Anyone walking along the River Teme has a chance of seeing these large insects and we would welcome any records. Please send them to Worcestershire Biological Records Centre. Size is important as other smaller skaters will use slow-flowing rivers, a photograph would help in determining records.
Southwood, T.R.E & Leston, D. 1959. Land and Water Bugs of the British Isles. Warne, London.
Further note: On 30th June 2014 Will Watson found River Skaters in Worcestershire (just!) on the River Teme at Westbrook near Berrington, SO55556773 (02). The picture also shows water beetle Platambus maculatus.
01. River skater Aquarius najas on River Teme. Brett Westwood
02. River skater Aquarius najas and water beetle Platambus maculatus. Will Watson.